Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
H,W = map(int,input().split())
src = [input() for i in range(H)]
walls = 0
for row in src:
    walls += row.count('#')

visited = [[0 for j in range(W)] for i in range(H)]
q = deque([(0,0,0)])
dxs = [1,0,-1,0]
dys = [0,1,0,-1]
while q:
    d,x,y = q.popleft()
    if (x,y) == (W-1,H-1):
        print(H*W - walls - d - 1)
        exit()
    for dx,dy in zip(dxs,dys):
        nx,ny = x+dx, y+dy
        if not(0 <= nx < W) or not(0 <= ny < H): continue
        if src[ny][nx] == '#' or visited[ny][nx]: continue
        q.append((d+1,nx,ny))
        visited[ny][nx] = 1

print(-1)